Form jack and hoist connector for stripping and lifting a masonry casting from a form

ABSTRACT

A form jack and hoist connector is described for use in freeing a concrete or similar masonry casting from a trough-like form in which it has been cast, whereby the form is stripped in the action of hoisting the casting for transfer of it to a point of storage or use. Castings such as those forming pre-built monolithic external cellar stairwells for attachment to subgrade foundation walls, unitized entrance landings and stairs, and the like, are typical of the kind of large heavy structures to be handled by the novel form jack. The jack consists of a central beam with projecting arms pivoted at each end. An integral eye or other means of attachment to a hoist rig is provided at the center of the beam. The free ends of the pivoted arms are adapted to be supported on portions of the form structure itself to serve as fulcrum points for leveraging the casting out of the form. Attachment means are provided intermediate the pivot point and free end of each arm to engage and lift the casting as the central beam member is hoisted, simultaneously prying the casting from the form in this lifting process.

Sept. 9, 1975 United States Patent 1 Lyons FORM JACK AND HOIST CONNECTOR[57] ABSTRACT A form jack and hoist connector in fr FOR STRIPPING ANDLIFTING A MASONRY CASTING FROM A FORM is described for use eeing aconcrete or similar maso a trough-like form in which it h nry castingfrom as been cast, whereby n of hoisting the cast- S U m 5 m 6 0 mn m Sn m f m mr 8 H d WR O t n e V n l M l the form is stripped in the actioing for transfer of it to a ings suc point of storage or use, Castuiltmonolithic exterent to subgrade foun- [22] Filed: Aug. 8, 1974 h asthose forming pre-b ar stairwells for attachm dation walls, unitizedentrance 1 Appl. No.: 495,373

nal cell andings and stairs, and

mum v ses Y m w k hum e m r 6 How 0M wm io kn eem mmw f 3% l a d mew .m.w m erl bo mm HMS.$ 6mm mmc m mfi %mc 56 2M6 R w l 8 m m 4 9 9 2 2 D An D B 7 n M u 4 u 9 u 2 m r C G QM L U .m N H 5 5 oted at each end. Aninte e or other means of attachment to a hoist rig is provided at thecenter of the beam. The free ends adapted to be supported on [58] Fieldof Search... 294/68, 67 R, 67 BC. 67 DA,

gral ey of the pivoted arms are portions of the form strucm points forture itself to serve as fulcru leveraging the casting out of the form.

vided intermediate the each arm to enga Attachment means are propivotpoint and free end of ge and lift the casting as the central 3/1942Nielsen 3/1944 6/1960 simultaneously prying the is lifting process.

beam member is hoisted i m m G casting from the form in th 4a t c n O sn c r 0 L Evon C. Blunk 7 Claims, 5 Drawing Figures Altorney. A

PATENTEB SEP 9l975 3,904,231

FORM JACK AND HOIST CONNECTOR FOR STRIPPING AND LIFTING A MASONRYCASTING FROM A FORM FIELD OF THE INVENTION The invention here relates toa device for facilitating the stripping of heavy cast masonry structuresfrom open-top forms in which they have been cast; and more particularly.to a form jack which engages a casting and uses the form itself as aleverage bearing point or fulcrum in the process of hoisting thecasting, whereby to pry the casting free of the form in the initiallifting or hoisting of it for transfer to a point of storage orplacement on a transport vehicle.

BAC KGROU N D OF TH E INVENTION Heavy masonry structures are commonlyfabricated as monolithic castings at a central processing plant, and arethen transported individually as needed to a construction site forerection. Typical of such structures are external cellar stairwells suchas those described in US. Pat. No. 3,307,308. These are precast ofpoured concrete in open-top trough-like forms such as the formsdescribed in US. Pat. No. 3,310,275. The forms are relatively large andexpensive and must accordingly be designed for repeated reuse. In orderto withstand the loading stresses and rough usage, the forms are ofextremely heavy metal construction. The assembly of them in preparationfor casting and the subsequent stripping of them from the cast productis timeconsuming, requires considerable manual labor, and increases thepossibility of damage to the components of the form or loss of bolts,clamps or other fastening elements used in holding the form in assembledcondition.

A principal objective of this invention accordingly is to facilitate theremoval of heavy precast concrete structures from the forms in whichthey have been cast. Other objectives include those of reducing theamount of manual labor required in this operation, and also of reducingthe possibility of damage to or loss of form components in theassembling/disassembling operations. It is a further purpose of theinvention to simplify the manner of attaching a hoist to such precaststructures so that they can be manipulated mote safely while being movedto and installed at a construction site.

SUMMARY OF THE INVENTION A hoist accessory is provided comprising a formjack having. a central beam member with provision for attachment theretoof a cable hook or other hoisting equipment. An arm is pivoted to eachend of the central beam. each such arm having a free end projectingaxially beyond the end of the beam. The span formed by the beam andcooperating arms is made slightly greater than the width of the face ofthe cast structure to be lifted so that the free ends of the armsoverlie the sides of the form. The free ends of the arms are eachprovided with a bearing pad or equivalent formation which permits it tobe rested on some portion of the form which is to be stripped from thecasting, whereby to provide a stationary fulcrum point for therespective arm as the central beam member is raised. Attachment means,such as a hook or jaw member is disposed adjacent the outer end of eacharm on the underside thereof for making attachment or engagement withthe casting to permit it to be lifted. In the initial stage of thehoisting operation, with this attachment means engaging the casting, thefulcrum points at the free ends of the pivoted arms are disposedslightly above the longitudinal axis of the central beam member. Thus,as the 5 jack is lifted, the central beam member pivots the inner endsof the arms upwardly relative to the outer fulcrum points, therebyprying the concrete casting upwardly relative to the form. Once thesurface contact at the in terface between the form and casting has beenbroken, the form is freed from the casting and the latter may be hoistedfor transfer to a storage point or to a transport vehicle. On settingthe casting down, the form jack can then be disengaged from the casting.

The invention is described in more detail in connection with theembodiments illustrated in the accompanying drawings in which FIG. 1 isa perspective view in side elevation showing a concrete cellar stairwellcasting being stripped from the sheet metal form in which it was made,using the novel form jack;

FIG. 2 is a fragmentary view of the jack showing one of its arm inarticulated position preliminary to hoistmg;

FIG. 3 is a end elevational view looking in the direction of arrows 3-3of FIG. 2;

FIG. 4 is a fragmentary perspective view of a modified form of form jackshowing a different type of means for engaging and lifting a casting;and

FIG. 5 is a fragmentary view in side elevation showing the form jack ofFIG. 4 in position to lift a casting from its form.

In FIG. 1 there is illustrated a trough-like plate or reinforced sheetmetal form F of the type shown for example in US Pat. No. 3,310,275 foruse in casting a monolithic concrete subgrade cellar entry stairwell.Concrete is poured into the open upper face of the form F and allowed toset to produce a finished casting C, only the upper face of whichappears in the drawing. Attachment loops L are imbedded in this upperface during the pouring or before the concrete has set, loops L beingdisposed slightly inwardly of opposite side walls of the casting C atthe approximate midor balance point of the casting. Loops L permitattachment of the form jack, indicated generally at 10 in the drawing,for the purpose of separating casting C from form F and hoisting thecasting free of the form.

Form jack 10 is composed of a central beam member I2 having an eye I4 orsimilar attachment means rigidly secured at the mid-point of the beam toreceive a hoist hook H attached by cable to a winch or other device forlifting the casting. As here shown, form jack 10 is built up from twoheavy angle irons 16, in back-toback spaced juxtaposition (see FIG. 3),being held in such relation by web plates 18 welded to the under facesand running transversely of the angle irons at either end.

An arm 20, comprising a heavy elongated metal plate, is received betweenthe upright legs of angle irons 16 at the opposite ends of the centralbeam member. Each of arms 20 is pivotally connected to beam 12 by pins22 and projects axially beyond the respective end of the beam. In thearrangement described, arms 20 are free to pivot upwardly relative tothe longitudinal axis of beam I2 but cannot pivot below that axisbecause of abutment against webs [8.

At the outer free end of each arm 20, a bearing pad 24 (shown as asocket member in this instance) is secured to the underedge of the arm.This is adapted to make bearing contact on a portion of form F so as toconstitute a vertically stationary fulcrum point, as will be describedmore fully presently, for arms 20. A rod R positioned along each sideface of form F is here illustrated as the fulcrum support, and itsprojecting upper end is received in socket 24 with a loose or sloppyfit. Such support rod arrangement is convenient, but any other rigidsupport member or portion of form F can be made to serve the purpose.

A hook 26 is carried by each arm 20, spaced intermediate the respectivebearing pad 24 and end of beam 12. Hooks 26 are adapted to engage loopsL in the upper face of the casting.

In preparing to hoist the casting from the form, form jack is placed onthe upper face of the casting with hooks 26 passing through loops L andbearing pads 24 resting on support rods R. Preliminary to hoisting, therelative position of the parts is shown more particularly in FIG. 2, inwhich it is seen that arms are pivoted slightly upwardly fromlongitudinal alignment with central beam 12. When lifting force isapplied to hoist hook H, central beam 12 pivots the inner ends of arms20 upwardly on pads 24 about the fixed fulcrum points provided by therods. Leverage is thus applied to hooks 26 which is transmitted throughloops L to pry the casting free of its form. Only a slight movement ofthe casting relative to the form is necessary to break the interfacecontact between the casting and form. Once this has occurred, casting Ccan be lifted free without further need for jacking or leverage action,and jack I0 thereafter serves merely as a hoist beam structure fromwhich the casting is suspended during transfer of it to a storage pointor transport vehicle.

In the modified structure shown in FIGS. 4 and 5, the principle ofoperation of the form jack is identical with that described above, but aslightly different arrangement is provided for effecting engagementbetween the casting and the form jack.

In this instance the means for engaging the casting comprises a pair ofpivoted dogs 126, one on each arm 120, taking the place of thecorresponding hooks in the structure described above. Each dog 126 ispivotally secured to an arm 120 to hang downwardly below the lower edgethereof. Each dog is formed with a claw 128 which serves as a means forengaging the casting.

In order to use the arrangement shown in FIGS. 4 and 5, provision mustbe made in form F for removing a small panel of the form wall at thecenter near the upper edge on each opposite side after the concrete hashardened. The arrangement is such that not only can the panel bewithdrawn easily after the casting has hardened. but it also serves toform in the side wall of the casting a depression with an overhanginglip which can be engaged by the claw of the corresponding dog 126 of theform jack.

When the casting is to be withdrawn from the form, jack is placed on thetop of the casting, with its bearing pads I24 resting on support rods Ror equivalent at opposite sides of the form. Arms I20 in this conditionare pivoted slightly upwardly at their outer ends above the longitudinalaxis of central beam 112. In this condition, dogs I26 tend to swing downby gravity to make engagement with the casting and the dog pivot is solocated that as the jack is raised, claws 128 are forced into clampingengagement with the sides of the casting beneath the overhanging lipsformed by the recesses (see FIG. 5 dotted line showing). In some casesit may be necessary in this arrangement to allow for lateral movement ofrods R; in which case. the rods need not be permanently secured to theside faces of the form. Continued lifting force applied to jack 110 prysor levers the casting free of interfacial contact with the form, therebystripping the form from the casting in the process of hoisting it.

What is claimed is:

l. A form jack for stripping a finished masonry casting from a form inwhich is has been poured, said jack comprising in combination:

a central beam member having attachment means centrally thereof forengagement by a hoist;

a pair of arms, each such arm being pivoted at its inner end to an endof said beam and projecting axially outward of such beam end;

bearing means at the projecting free end of each arm for making bearingengagement with a portion of the form to be stripped from the casting;and

attachment means on each arm. located intermediate its respective freeend bearing means and end of said central beam, for engaging andsupporting the casting.

2. A form jack as defined in claim 1, wherein one of said beam and armmembers is provided with a projection which prevents the arm member frompivoting below the level of the beam axis, while permitting free pivotalmovement above such axis.

3. A form jack as defined in claim 2, wherein said beam has a lowerflange member, and said arms are each pivotally connected to said beamabove said lower flange member inwardly of the end thereof.

4. A form jack as defined in claim I, wherein said bearing means at thefree end of each arm is a jack pad.

5. A form jack as defined in claim 1, wherein said bearing means at thefree end of each arm is a post member extending downwardly forengagement with a portion of the form to be stripped from the casting.

6. A form jack as defined in claim 1, wherein said attachment means oneach arm is a pivoted hook 7. A form jack as defined in claim I, whereinsaid attachment means on each arm is a pivotable dog jaw.

1. A form jack for stripping a finished masonry casting from a form inwhich is has been poured, said jack comprising in combination: a centralbeam member having attachment means centrally thereof for engagement bya hoist; a pair of arms, each such arm being pivoted at its inner end toan end of said beam and projecting axially outward of such beam end;bearing means at the projecting free end of each arm for making bearingengagement with a portion of the form to be stripped from the casting;and attachment means on each arm, located intermediate its respectivefree end bearing means and end of said central beam, for engaging andsupporting the casting.
 2. A form jack as defined in claim 1, whereinone of said beam and arm members is provided with a projection whichprevents the arm member from pivoting below the level of the beam axis,while permitting free pivotal movement above such axis.
 3. A form jackas defined in claim 2, wherein said beam has a lower flange member, andsaid arms are each pivotally connected to said beam above said lowerflange member inwardly of the end thereof.
 4. A form jack as defined inclaim 1, wherein said bearing means at the free end of each arm is ajack pad.
 5. A form jack as defined in claim 1, wherein said bearingmeans at the free end of each arm is a post member extending downwardlyfor engagement with a portion of the form to be stripped from thecasting.
 6. A form jack as defined in claim 1, wherein said attachmentmeans on each arm is a pivoted hook.
 7. A form jack as defined in claim1, wherein said attachment means on each arm is a pivotable dog jaw.